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In this study, a novel NiCuZn (Ni 0.24 Cu 0.21 Zn 0.55 Bi x Fe 2- x O 4 (x = 0,0.025, 0.050, 0.075)) ferrite composition (Ni/Zn molar ratio is 24/55) was successfully prepared by the addition of Bi3+ ion for substitution. It is demonstrated that Bi 2 O 3 served as an effective doping agent to reduce the sintering temperature to 900 °C and enhanced the high-frequency magneto-dielectric properties. Notably, the maximum permeability is ∼118 (@ 13.56 MHz) when x = 0.050 with a cut-off frequency of 47 MHz, which is nearly four times higher than that of the unsubstituted sample. In addition, an NFC antenna employing optimized ferrite as an electromagnetic shield sheet was designed and simulated. The results indicated that the chaotic and weakened magnetic field was recovered, and the biased resonant frequency was restored from 31.87 MHz to 13.68 MHz. These findings hold significant scientific importance and practical value in achieving superior electromagnetic shielding performance and miniaturization in NFC system. [Display omitted] [ABSTRACT FROM AUTHOR]

A graphene quantum dot (GQD)-decorated ZnFe2O4 hybrid nanocomposite [GQD-ZHN] was synthesized using the sol–gel technique. In the X-ray diffraction (XRD) analysis, a cubic spinel structure was identified with the space group Fd-3 m. Fourier-transform infrared (FT-IR) analysis revealed the vibration bands of the samples, while the existence of GQDs in GQD-ZHN was confirmed by the Raman spectra. Field emission scanning electron microscopy (FESEM) provided insights into the microstructural morphological topology of the surface. The dielectric properties of GQD-ZHN were analysed with respect to their dependence on frequency and temperature and explained by Maxwell–Wagner-type polarization. The frequency-dependent ac conductivity (σac) followed Jonscher's power law and investigated the dynamics of ion hopping in GQD-ZHN. Impedance and modulus spectroscopy were used to further evaluate electrical characteristics such as relaxation time (τ). Nyquist plots have been used to estimate grain and grain boundary contributions. The GQD-ZHN exhibited superparamagnetic properties at room temperature. At room temperature, GQD-ZHN exhibited a strong magneto-dielectric coupling (MD) and showed negative magneto-dielectric properties in low-frequency regions. These properties of GQD-ZHN enable it to be used as a potential application in microelectronic systems, spintronics and memory devices. [ABSTRACT FROM AUTHOR]

we deeply dived multi-phase-based 0.16BaFeO3-0.84MgFe2O4 ferrite for VHF antennas. The structural and magneto-dielectric properties synthesized at various temperatures (1100 °C, 1125 °C, 1150 °C and 1175 °C) were investigated. The results demonstrated the coexistence of hexagonal and cubic spinel phases. Microstructure analysis indicated higher temperature induced lager grain size and denser structure. Meanwhile, both the saturation magnetization (from 28 to 25 emu/g) and coercivity (19–5 Oe) decreased. In addition, real permeability (μ′) and permittivity (ε′) arose at higher temperature, promising equivalent permeability and permittivity. What's more, relatively low magnetic and dielectric losses (tanδμ ∼10−2 to 10−3 and tanδε ∼10−3 to 10−4) promote low energy loss. Finally, a miniaturized antenna with relative bandwidth of 14.6 %, peak gain of 0.98 dB, and radiation efficiency of 74.6 % was simulated based on the processed ferrites. In conclusion, the presented investigation greatly improves the magneto-dielectric response, which paves the way to realize high performance in VHF antenna application.

In this study, the influence of magnetic content of NiFe1.93Dy0.07O4 spinel ferrite on the structural, morphological, optical, and magneto-dielectric properties of BaTiO3 materials was investigated. NiFe1.93Dy0.07O4 magnetic nanoparticles and BaTiO3 dielectric materials were firstly synthesized using the hydrothermal method and sol–gel auto-combustion route, respectively. Then, different contents of the magnetic nanoparticles were added to BaTiO3 to form a series of BaTiO3/(NiFe1.93Dy0.07O4)x samples (abbreviated as BTO/(NDFO)x) with x = 0, 2, 5, 10, 20, and 100 %. The analysis of the structure via X-ray diffraction (XRD) technique revealed a transformation from a tetragonal structure for the pristine BTO sample to a cubic structure upon the inclusion of magnetic nanoparticles. The morphological observations and chemical composition analyses via scanning electron microscope (SEM) coupled with EDX system showed the successful formulation of biphasic products. The optical properties were investigated, and it was found that the inclusion of the magnetic phase diminishes the bandgap energy (Eg) of final BTO/(NDFO)x samples. Furthermore, vibrating sample magnetometer (VSM) was used to investigate the magnetization properties. The values of saturation magnetization (MS) and remanent (Mr) magnetization are rising with the increase of magnetic phase content. However, the coercivity (Hc) does not show a regular variation with the increase of NDFO content. The dielectric properties were also investigated for different BaTiO3/(NiFe1.93Dy0.07O4)x samples. The obtained results showed that the real permittivity (ε′) and dielectric tangent loss (tan δ) increased with increasing temperature. Remarkably, the addition of magnetic content provokes a reduction in tan δ values compared to the pristine BTO sample. The lowest values of tan δ and highest frequency stability were noticed in the sample added with 10 % of magnetic phase. The impedance and modulus were also determined and discussed. [ABSTRACT FROM AUTHOR]

Two phase-based composites comprising barium titanate (BaTiO 3) and spinel magnesium ferrite (1- x)Mg 0.7 Cd 0.3 Fe 2 O 4 + x BaTiO 3 (x = 0.00, 0.03, 0.06, 0.09, and 0.12) were investigated. The phase structure revealed the coexistence of the perovskite BaTiO 3 and spinel MgFe 2 O 4 phases. The microstructural analysis indicated that the average crystallite size initially increased and then decreased, as the increase in x weakened magnetisation, decreased saturation magnetisation (from 47.5 to 35.9 emu/g) and coercivity (150–0 Oe) were obtained, resulting in reduced permeability at low frequency. The permittivity gradually increased owing to tuning by barium titanate, which has strong dielectric properties, promising a relatively large miniaturisation factor. Further, low magnetic loss (tan δ μ ∼10−2) and dielectric loss (tan δ ε ∼ 10−2 to 10−3) guarantee high quality factor. The low losses and enhanced dielectric properties of the as-synthesised composites could be conducive to improving the behaviour of such magneto-dielectric composite systems in microwave applications. [ABSTRACT FROM AUTHOR]

A series of Ba1.5Sr1.5Co2+xZrxFe24‐2xO41 hexaferrites (x = 0.00, 0.01, 0.03, 0.05, 0.07, and 0.09) were successfully prepared by the conventional solid‐state reaction method. It was found that as the Co2+ and Zr4+ ions entered the hexaferrite structure, the lattice parameters increased, whereas the relative density increased when x = 0.00‐0.03 and then decreased. A suitable amount of substitution increased the DC resistivity, reduced the magnetic and dielectric losses, and made the μ′$\mu ^{\prime}$ and ε′$\varepsilon ^{\prime}$ closer to each other. At x = 0.03, the relative density and DC resistivity of the samples reached their maxim. Besides, both the magnetic and dielectric losses were lowest within the frequency range of 10 MHz‐1 GHz. Meanwhile, the hexaferrite was impedance matched to free space, and the miniaturization factor was about 15. Therefore, this low‐loss ferrite with almost equal permeability and permittivity could be meaningful for antenna miniaturization and high‐frequency applications. [ABSTRACT FROM AUTHOR]

The U-type hexaferrites ([Formula: see text][Formula: see text]Co2[Formula: see text][Formula: see text] ([Formula: see text] 0, 0.05, 0.10, 0.15, 0.20, 0.25) have been synthesized by auto-combustion method. The work involves the study of structural, microstructural, dielectric, magnetic and magneto-dielectric properties of the prepared materials. The structural analysis has been done by X-ray diffraction technique along with Le Bail refinement which confirmed the pure hexagonal phase for all the samples. The microstructural analysis has been carried out by field-emission scanning electron microscopy. The vibrating sample magnetometer is used to measure the magnetic properties. The sample with a composition of [Formula: see text] 0.15 has shown the maximum magnetization of approximately 73.31 emu/g with the remnant magnetization of 38.89 emu/g and coercive field of 1.77 kOe at room temperature. Moreover, the same sample has delivered the maximum magneto-dielectric response of about 54.18% at 1.5-T field.

The U-type hexaferrites ( Ba 1 − 3 x La 2 x ) 4 Co2 Fe 3 6 O 6 0 (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25) have been synthesized by auto-combustion method. The work involves the study of structural, microstructural, dielectric, magnetic and magneto-dielectric properties of the prepared materials. The structural analysis has been done by X-ray diffraction technique along with Le Bail refinement which confirmed the pure hexagonal phase for all the samples. The microstructural analysis has been carried out by field-emission scanning electron microscopy. The vibrating sample magnetometer is used to measure the magnetic properties. The sample with a composition of x = 0.15 has shown the maximum magnetization of approximately 73.31 emu/g with the remnant magnetization of 38.89 emu/g and coercive field of 1.77 kOe at room temperature. Moreover, the same sample has delivered the maximum magneto-dielectric response of about 54.18% at 1.5-T field. [ABSTRACT FROM AUTHOR]

The influence of temperature, magnetite shape, and content on the electromagnetic interference shielding properties was determined for dextrin based composites. The absorption properties increase linearly with increasing temperature. The usage of dextrin results in the widening of the absorption frequency region in comparison to the pure magnetite nanoparticles. The composite containing 50 wt% of spherical Fe3O4 NPs has RL

A sol-gel synthesis method was used for the synthesis of pure CoFe 2 O 4 (CFO) as well as Graphene Quantum Dots (GQDs) decorated CoFe 2 O 4 Hybrid Nanocomposite (GCHN). From X-ray diffraction (XRD) data it was analyzed that both these samples have a cubic structure with Fd-3m space group. Using Debye-Scherer's equation, the average sizes were determined to be 24.48 and 13.74 nm, respectively. FTIR spectra revealed details about vibration bands and functional groups present. Raman spectra confirmed existence of GQDs in GCHN with an I D /I G ratio of ∼0.8. The results of Field emission scanning electron microscopy (FESEM) analysis exhibited microstructural morphological details having shapes of grains to be non-uniform in shape. UV–visible data was used to calculate band gap (E g) energy by using Tauc plot method and found to be 2.52 eV and 2.99 eV respectively for CFO and GCHN. Urbach energy (E U) was found to be 1.03 and 1.19 eV for CFO and GCHN respectively. The dielectric properties of GCHN were analyzed for dependence on frequency and temperature and explained by Maxwell-Wagner-type polarization. The frequency-dependent ac conductivity (σ ac) followed Jonscher's power law and investigated dynamics of ion hopping. Impedance spectroscopy was used to further evaluate Nyquist plots with respect to temperature as well as magnetic fields to estimate grain and grain boundary contributions. This was further used to evaluate electrical characteristics such as relaxation time (τ). Activation energies (E a) calculated using relaxation times were found to be 0.48 eV for CFO while 0.22 and 0.92 eV for GCHN respectively. At room temperature, CFO and GCHN exhibited a strong magneto-dielectric coupling (MD) and showed negative magneto-dielectric properties in low-frequency regions. At room temperature (RT), magnetization values of CFO and GCHN displayed were 38.48 and 7.52 emu/g respectively. The lower magnetization value was possibly due to shielding by GQDs in GCHN. These properties enable it to be used as a potential application in microelectronic systems, spintronics, optical and optoelectronic devices, magnetic resonance imaging (MRI) and memory devices. (a) XRD pattern, (b) Frequency dependence ε at diverse temperatures (300–773 K) [Inset shows temperature dependence ε at various frequencies between 100 Hz and 1 MHz], (c) Magneto-Dielectric (MD %) coupling at diverse magnetic fields varying from 0.0 T to 1.5 T and (d) Nyquist plot of Z′ and Z″ data in between 0.0 T and 1.5 T for GCHN [ G QDs/ C oFe 2 O 4 H ybrid N anocomposite]. [Display omitted] • GQD-C oFe 2 O 4 H ybrid N anocomposite (GCHN) were synthesized using sol-gel method. • E g obtained was found to be 2.52 and 2.99 eV respectively for CoFe 2 O 4 and GCHN. • GCHN exhibited negative magneto-dielectric (MD%) and negative magneto-loss (ML%). • Impedance spectroscopy was used to further evaluate using Nyquist plots. • Magnetization value of GCHN decreased abruptly due to shielding of GQDs in GCHN. [ABSTRACT FROM AUTHOR]

La-Zn substituted Ba2Co2Fe12O22 (Co2Y) hexagonal ferrite was synthesized using a conventional solid-state method with composition Ba2−xLaxCo2Fe12−xZnxO22, where x equals 0.0, 0.1, 0.3 and 0.5. The phase formation behavior and changes in the crystal structure of the substituted ferrite were investigated using x-ray diffraction (XRD) analysis. Accurate lattice parameters were evaluated through Rietveld refinement of the XRD pattern. XRD, as well as energy dispersive spectral analysis, showed the formation of a lanthanum iron oxide phase in x = 0.3 and 0.5 compositions. There was a small increase in unit cell volume with the substitution. The microstructural analysis showed a decrease in grain size with increasing substitution. The magnetic properties; Ms, Mr, and Hc of the ferrite were measured and found to increase with increasing substitution. Permittivity and permeability were measured and found in the range 10-16. It can be concluded that the La-Zn substitution was an effective method for improving magnetic and dielectric properties of the Co2Y ferrite. [ABSTRACT FROM AUTHOR]

Composites of ferroelectric and magnetostrictive materials show more magnetoelectric coupling than single phase materials. Core–shell CoFe 2 O 4 :BaTiO 3 nanocomposites (1:1 weight ratio) and a mixture of both of them have been synthesized by a combination of hydrothermal and sol gel techniques. X ray diffraction analysis confirms the presence of both the materials in the samples. High Resolution Transmission Electron Microscope images confirm the core shell structure. The magnetoelectric coupling effect is investigated by measuring the magnetoelectric coefficient. It is observed that the coefficient is 35 times larger in the core–shell nanocomposites compared to that of the mixture. [ABSTRACT FROM AUTHOR]